In general, there are several kinds of DC motors. Among them, a brushless DC (BLDC) motor forms a magnetic field of a predetermined size and direction to rotate a rotor.
As shown in FIG. 1, a conventional BLDC motor is provided with a rotor R, a stator S, and an air gap 15. The rotor R is provided with a permanent magnet 11 and a rotor core 12. The stator S forms a rotating magnetic field in order to develop a desired speed and torque, and is provided with armature coils 13 and an armature yoke 14. The air gap 15 is located between the stator S and the rotor R, and it changes electrical energy into kinetic energy and delivers the kinetic energy.
Moreover, as shown in FIG. 2, the conventional BLDC motor is provided with a hall sensor 17. The hall sensor 17 senses a relative location of the permanent magnet 11 with respect to each of armature coils 13. Accordingly, since the stator S has an appropriate amount of electricity input thereto, a high torque which can be controlled is produced from the stator S.
A conventional BLDC motor as described above is assembled as follows.
For assembly of the stator, an armature yoke 14 and an armature coil 13 are prepared. In particular, an armature yoke 14 formed of ferromagnetic materials may be prepared as a block or pile type. A nonconductor 16 is located between the armature yoke 14 and the armature coils 13. The armature coils 13 are bonded to the nonconductor 16 by an adhesive material such that the armature coils 13 are arranged with predetermined gaps therebetween (as an example, equal gaps). The armature coils 13 are assembled with the armature yoke 14, and then the stator S is molded with an epoxy so as to enhance weatherproof properties thereof.
For assembly of the rotor, a permanent magnet 11 and a rotor core 12 are arranged together. In particular, the permanent magnet 11 is arranged as a segmented or ring shape, for example. An inner circumference of the permanent magnet 11 and an outer circumference of the rotor core 12 are bonded to each other with an adhesive material.
A hall sensor 17 is assembled on a PCB (printed circuit board) formed with a pattern which is predetermined on the basis of a constant of a stator and a magnetic pole number of a rotor. Such hall sensor 17 is assembled on/at the stator S with an adhesive material or a bolt, for example.
However, conventional BLDC motors as described above have certain problems. For example, assembly of the armature coils 13 is the most important determinant of efficiency of a BLDC motor. That is, when the distance between the armature coils 13 is fixed, the assembly is deemed to be perfect. However, according to the conventional BLDC motor, the distance between armature coils 13 is not fixed. Consequently, the conventional BLDC motor has a problem in that a torque ripple phenomenon is manifested due to an unequal rotating magnetic field. That is, vibration and/or noise occur, or efficiency of the BLDC motor is deteriorated.
In addition, since the distance between the armature coils 13 is not fixed, the conventional BLDC motor has a problem in that a weak part is present after the stator S is molded by an epoxy. Consequently, because of insulation failure at the weak part, a shorting phenomenon of armature coils occurs.
In addition, because assembly quality of the armature coils 13 is dependent on worker proficiency, the conventional BLDC motor has a problem in that productivity is deteriorated and inferior goods are mass-produced.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known in this country to a person of ordinary skill in the art.